Not an easy task, but definitely doable with some work and help from Heaven.
One suggestion that comes to mind is to look through the Peasch section of the Ohr Somayach website www.ohr.edu and see for yourself what you think might be helpful in the situation you describe, knowing the individuals involved. I particularly suggest the articles by Rabbi Orlofsky and Rabbi Milevsky. Please check them out (Passover Today, The Four Sons and Devolution, etc.).
Another idea is to obtain a copy of the very artistic and educational Haggada by Baruch Chait. It should be available in Jewish bookstores (it's large and the drawings are amazing). Just looking at it makes a person feel a special experience in my opinion.
Not specific to Passover, but very helpful in general is a new book called Gateway to Judasim by Rabbi Mordechai Becher. It is already a classic, and is written for someone non-practicing to help understand the whats, whys and hows of Judaism - written in a clear, intelligent and entertaining manner.
I wish you a wonderful, happy and meaningful Passover - all of you!